The present invention relates to a probe card used when inspecting a semiconductor device.
A probe card having probe needles is used to inspect a semiconductor device. Due to the miniaturization and high integration of recent semiconductor devices, the distance between bonding pads or inspection pads have become small. Further, the quantity of pads has increased. As a result, the probe needles must be arranged on the probe card in a concentrated manner. Further, to reduce inspection costs, a plurality of semiconductor devices may have to be inspected at the same time with the same probe card. This further increases the quantity of probe needles on the probe card, which, in turn, further increases the concentration of the probe needles. Under such a circumstance, probe needles affect one another when they are closely arranged. This produces noise, such as crosstalk. Accordingly, there is a demand for a probe card and probe needles that suppress the effect of noise without decreasing the concentration of the probe cards.
FIGS. 1 and 2 show a prior art probe card 5 provided with cantilever type probe needles. The probe card 5 includes a disk-shaped substrate 1. A hole extends through the central portion of the substrate 1. The substrate 1 includes a needle seat 3 and a support 4, which is made of synthetic resin and is located inward from the needle seat 3 and around the hole. A plurality of probe needles 2 extend outward in the radial direction from the central portion of the substrate 1.
Each probe needle 2 has a basal portion soldered to the needle seat 3 and a distal portion held by the support 4. The distal portions of the probe needles 2 are concentrated at the central portion of the substrate 1. Each probe needle 2 has a cantilever structure in which it becomes farther from the substrate 1 towards its distal end. Further, each probe needle 2 has a middle portion that is covered by an insulative tube to prevent electric connection with an adjacent probe needle.
To inspect a semiconductor device with the probe card 5, the distal end of each probe needle 2 is pressed against a pad of the semiconductor device.
In the probe card 5, a gap is formed by each probe needle 2 between the needle seat 3 and the support 4. Thus, as the quantity of probe needles increase, closely arranged probe needles affect one another and may pick up noise such as crosstalk. Further, in a probe card that inspects a plurality of semiconductor devices at the same time, the probe needles may be closely arranged to one another in the vertical direction with respect to the surface of the substrate. In this case, the probe needles would pick up even more noise.
Accordingly, such noise may reduce the inspection accuracy. Further, re-inspection may become necessary. This would prolong the inspection time.
To reduce the effect of noise in such probe needles, a probe card having probe needles with coaxial structures has been proposed. A probe needle having a coaxial structure includes a central conductive body, an insulative tube that covers the middle portion of the central conductive body, and a conductive metal tube (outer conductive body) that covers the insulative tube.
The two ends of the outer conductive body are connected to a ground wire on the substrate. Thus, the outer conductive body functions as a shield layer. This reduces the effects of noise.
Japanese Laid-Open Patent Publication Nos. 8-22463 and 2-50452 describe an example of a probe card including probe needles with coaxial structures.